This invention relates generally to a system and method for viewing objects normally obscured from vision by intense plasmas or flames. The invention is particularly applicable to electric arc welding where details of the welding pool, electrode, weld joint are concealed by the luminescent cloud of the welding plasma.
In both manual and automatic welding, welding quality can be improved by real-time sensory information about a variety of weld site parameters, including diameter and depth of the molten welding pool, temperature gradients around the pool, position of the pool vs the welding seam or previous weld beads, contamination or slag in the welding pool, and the degree of wetting at the weld pool/solidus interface. These parameters and others are observed or inferred in the manual welding process, primarily by means of the welder's vision. Hearing also plays a role in monitoring the dynamics of the welding arc.
A variety of sensory techniques have been used in automatic welding as a replacement for the manual welder's vision. However, as the trend continues towards autogeneous welding (automatic welding free from preprogramming by external sources), the welder's vision cannot be replaced but must instead be duplicated to some degree by the use of electronic vision, small computers, and image processing software. This approach would generally involve the use of a miniature video camera or solid-state optical detector array and appropriate optics which must be carefully integrated into the design of the welding torch.
One current example is the General Electric Weldvision.TM. system, which was developed by Richard W. Richardson at Ohio State University and commercialized by General Electric. It is designed for the gas-tungsten arc welding process (GTAW) in which a tungsten electrode is used to create the arc and the electrode and weld site are protected from oxidation by use of an inert purge gas. The vertical electrode is enclosed by a tubular shroud (or "gas cup") and the purge gas flows through the shroud from above and onto the welding site. Richardson devised an optical system coaxial with the electrode to acquire an image, which in turn is relayed by a fiberoptic bundle to a small solid-state CID video camera. His viewing geometry is attractive, first, because it provides a direct overhead perspective of the entire welding pool and, secondly, because the welding electrode provides blockage of light from the brightest portion of the welding arc and thereby improves the quality of the video image. This system is used primarily to obtain video data describing weld pool diameter and position relative to the prepared welding groove. The groove location is revealed by two parallel laser stripes beamed onto the weld joint in advance of the welding pool. This system accomplishes true automatic welding, but is limited to single-pass welding because the guidance signature from the groove is destroyed during the first welding pass.
Another welding process, important for its use in heavy construction, is gas-metal arc welding (GMAW). The GMAW process is similar to GTAW, however, the tungsten electrode is replaced by a consumable wire electrode, which provides the filler material for the weld. This process applies metal at higher rates at less power, but creates a greater threat to optical components, with much higher levels of spattering metal.
Therefore, it is an object of the present invention to provide a system and method to generate electronic imagery for automatic control of multiple-pass welding processes.
It is another object of the present invention to provide a system and method for acquiring high-definition imagery of objects obscured by intense plasmas or flames, such as welding sites.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.